1. Technical Field
The present invention relates to semiconductor manufacturing in general, and, in particular, to a method for manufacturing polysilicon resistors. Still more particularly, the present invention relates to a method for manufacturing silicide-interface polysilicon resistors.
2. Description of Related Art
Semiconductor device fabrication involves a variety of processes and operations. Such operations include, but are not limited to, layering, doping, heat treatments, and patterning. Layering is the operation used to add layers of a selected thickness to a wafer surface. The layers can be insulators, semiconductors, and/or conductors, which can be grown or deposited by a number of suitable methods such as chemical vapor deposition, sputtering, etc.
Doping is the process that introduces specific amounts of dopants in the wafer surface through openings in surface layers. Two general techniques of doping are thermal diffusion and ion implantation.
Heat treatments are operations in which a wafer is heated and cooled to achieve specific results. Generally, no additional material is added although contaminates and vapors may evaporate from the wafer surface. A common heat treatment is called an anneal that is typically employed to repair damage to crystal structures introduced by ion implantation.
Patterning is the operation that employs a series of steps that results in the removal of selected portions of added surface layers. The series of steps include forming a layer of resist or photoresist over a semiconductor device. Then, a resist mask or reticle is aligned with the semiconductor device. Subsequently, the layer of resist is exposed or irradiated through the resist mask, which selects portions of the layer of resist that are later removed to expose underlying portions of the semiconductor device. A fabrication process, such as ion implantation, ion diffusion, deposition, and/or etching, can then be performed on exposed portions of the semiconductor device.
Semiconductor devices typically include transistor and resistors. Many transistors have gate electrodes formed with polysilicon material. Similarly, many resistors are also formed with polysilicon material and are commonly referred to as polysilicon resistors or poly resistors.
Because of the continued demand in reducing the size of semiconductor devices, it is desirable to provide a highly resistive polysilicon resistor having a relatively small footprint.